CONTRIBUTION OF VENTRAL TEGMENTAL AREA DOPAMINE NEURONS TO EXPRESSIONOF CONDITIONAL FEAR - EFFECTS OF ELECTRICAL-STIMULATION, EXCITOTOXIN LESIONS, AND QUINPIROLE INFUSION ON POTENTIATED STARTLE IN RATS

Potentiated startle was used in this study to determine the fear-motiv ational functions of the ventral tegmental area (VTA). In Experiment 1 , electrical stimulation of the VTA increased acoustic startle amplitu des. In subsequent experiments fear-potentiated startle was assessed f ollowing axon-sparing N-methyl-D-aspartic acid (NMDA) lesions of the V TA and after bilateral intra-VTA infusion of the dopamine (DA) D-2/3 r eceptor agonist quinpirole. The NMDA lesions produced substantial cell loss in the medial ventral tegmentum and suppressed fear expression. Similarly, inhibition of DA neuronal activity associated with locally administered quinpirole blocked fear-potentiated startle. It was sugge sted that VTA neurons and their forebrain DA projections regulate leve ls of aversive emotional arousal within the amygdala-based fear system .